Scalable Vector Graphics (SVG) is a vector image format for two-dimensional graphics. It is widely supported by modern web browsers and is fully integrated into the browser document object model (DOM), along with other technologies such as Hypertext Markup Language (HTML) and Cascading Style Sheets (CSS). In SVG, in contrast to how location relative the x-axis and y-axis is explicitly expressed there is no precise way to express location on the z-axis of an image. Indeed, there is no concept of z-order, meaning depth of elements. Image elements are simply layered on top of one another in the order they are encountered in the DOM. This does not present a problem for many web applications, which involve merely presenting graphics to a user. However, recently more web applications have permitted interactivity with the graphics. Such interactivity is limited, however, by the lack of an ability to move an image element along the z-axis.